Hate to ask this, but how often is he getting out? Lots of exercise cut down Buster's chewing by about half. We gave him a few more toys (helped a little), and got consistent about punishing him for chewing (helped a lot). We still lose about a shoe a year, but this is much better than it used to be.

By the way, putting pepper in the shoes didn't help at all. Buster treated them like a snuff box.